Truck frames must be especially rugged due to their utilitarian function. Off-highway trucks, which are used extensively for earth-moving operations, tend to require even more rigid frames to handle loads that can exceed thirty tons. The frames must handle both static and dynamic loads. These loads are typically a combination of bending, transverse and torsional loads. To provide transverse rigidity between the front wheels, prior frameworks have used a circular-shaped cross support, commonly referred to as a "horse collar". A horse collar extends in circumposing relationship about the engine. The horse collar carries the large moment forces caused by the cantilevered relation of the wheels to prevent torsional bending of the opposite main side rails of the framework. However, the presence of such horse collars makes the engine extremely difficult to service and essentially impossible to remove without first removing a portion of the horse collar to permit the necessary access to the engine.
A modified horse collar design is disclosed in U.S. Pat. No. 3,977,489 to Cole et al., entitled "Framework For A Wheeled Self-Propelled Truck," in which the framework includes a pair of longitudinally disposed, laterally spaced main side rails. A superstructure provides an upper, transverse bridgework interconnecting the side rails to add transverse rigidity in a manner which does not obstruct overhead accessibility to the engine. The superstructure also provides radial support for the upper ends of front suspension struts to minimize twisting of the main side rails by moment loads created by the wheels.
Another common truck frame is a "ladder type" frame which provides two longitudinal frame members connected by two transverse frame members. The ladder type frame provides torsional stability and is easily constructed. However, the generally rectangular shape of the frame diminishes the steering capability of the truck. An example of a modified ladder type frame is illustrated in U.S. Pat. No. 3,786,889 to Kelley, and entitled "Steerable Load Transporting Vehicle." The main frame members extend longitudinally of the vehicle and converge toward each other at an acute angle proceeding toward the forward end of the frame. This wedge shape allows the wheel assemblies to be steered through a greater angle. Still, either a ladder type frame or a frame with a horse collar involve a great deal of material cost and weight. Moreover, prior art frames, such as those described, are typically limited to use with a single engine.
Therefore, a need exists for an off-highway vehicle frame that is lighter, less expensive, and more efficient than conventional frames of similar function and capacity. The frame should be more efficient in terms of increased torsional stiffness per pound of frame weight. The frame should also connect the various necessary components comprising the vehicle with a minimum amount of joints and material. Additionally, the frame should be capable of, but not limited to, use with two separate diesel engines mounted side-by-side, as well as to the use of an A-frame and strut-type suspension arrangements.